#include <iostream>
#include <assert.h>
#include <cstdio>
#include <unistd.h>
#include <cstring>
#include <sys/types.h>
#include <sys/wait.h>

using namespace std;

int main()
{
    // 1.创建管道
    int pipefd[2] = {0};
    int n = pipe(pipefd);
    assert(n != -1);
    (void)n;

#ifdef DEBUG
    cout << "pipefd[0]" << pipefd[0] << endl;
    cout << "pipefd[1]" << pipefd[1] << endl;
#endif

    // 2.创建子进程
    pid_t id = fork();
    assert(n != -1);
    if(id == 0)
    {
        //子进程 - 读
        // 3. 构建单向通信的信道，父进程写入，子进程读
        // 3.1 关闭子进程不需要的fd

        close(pipefd[1]);
        char buffer[1024];
        while(true)
        {
            ssize_t s = read(pipefd[0],buffer,sizeof(buffer)-1);
            if(s > 0)
            {
                //读成功
                buffer[s] = 0;
                cout << "child get a message [" << getpid() << "] Father#" << buffer << endl;
            }
            else if(s == 0)
            {
                cout << "writer quit(father),me quit!!!" << endl;
                break; 
            }
        }

        close(pipefd[0]);
        exit(0);
    }

    // 父进程 - 写
    // 3. 构建单向通信的信道
    close(pipefd[0]);
    string message = " 父进程，我正在给你发消息";
    int count = 0;
    char send_buffer[1024];
    while(true)
    {
        // 3.2 构建一个变化的信息
        snprintf(send_buffer,sizeof(send_buffer),"%s[%d] : %d",message.c_str(),getpid(),count++);
        // 3.3 写入
        write(pipefd[1],send_buffer,strlen(send_buffer));
        // 3.4 sleep()
        sleep(1);
    }

    pid_t ret = waitpid(id,nullptr,0);
    assert(ret == 0);
    (void)ret;

    close(pipefd[1]);

    return 0;
}